1. Field of the Invention
The present invention relates to a lens apparatus which includes a splitting optical unit disposed in an optical path of an imaging optical system and which performs automatic focus control using a light flux from the splitting optical unit. The present invention also relates to an imaging apparatus including the lens apparatus.
2. Description of the Related Art
Conventionally, various automatic focus control techniques for imaging apparatuses, such as still cameras or video cameras, have been proposed. For example, Japanese Patent Application Laid-Open No. 2002-365517 discusses a lens/imaging apparatus which includes a splitting unit and a focus detection unit. The splitting unit is disposed in an optical path of an imaging optical system, and the focus detection unit is disposed in a split optical path generated by the splitting unit.
With respect to broadcast zoom lenses, for example, a lens apparatus disclosed in Japanese Patent Application Laid-Open No. 3-34781 has been known. The lens apparatus includes a focus lens unit, which is an anterior lens unit, and a macro lens unit, which is a part of a relay optical system. The macro lens unit is driven, independent from the focus lens unit, along an optical axis to perform focus control and to enable close-up photography.
In the above-described lens/imaging apparatus, automatic focus control is performed by detecting a focusing state using a split light flux obtained by the splitting unit. During the focus control, the relationship in a focal plane between an imaging unit and a focus detection unit is held constant.
However, in a case where close-up photography is performed with a macro lens unit disposed on the image side of the splitting unit, as discussed in Japanese Patent Application Laid-Open No. 3-34781, the relationship in a focal plane between the imaging unit and the focus detection unit may vary due to the movement of the macro lens unit. Therefore, correct automatic focus control may not be performed.
In addition, for special use of the macro lens unit, the macro lens unit can be used when a user wants to intentionally take a blurred image so as to obtain a special image effect. However, when the macro lens unit is used to perform blur photography, an operational characteristic different from that in close-up photography is required. More specifically, a focusing operation is required such that the amount of blurring increases in proportion to the amount of operation of the macro lens unit and an original object becomes in focus in response to the macro lens unit returning to its initial position.